Over at conversations, Microsoft mobile has mentioned in an article that,
If you are registered to Windows Phone Developer Preview Program, you might need to use the Nokia Software Recovery Tool to return your Lumia to a normal commercial software before downloading the Lumia Cyan update.
Now, we understand here that ordinary customer Lumia devices with Windows Phone 8.1 developer preview will get “Lumia Cyan” firmware normally and we have information about many Lumia 625 and Lumia 925 with WP8.1 dev preview getting Lumia Cyan firmware OTA.
Issue is with corporate Lumia users with BitLocker encryption. Those enterprise customers which have BitLocker encryption enabled may need to use Nokia Software Recovery Tool to return to the latest software + firmware version, before updating to Lumia Cyan.